Empty GIF generator not actually empty

Igor Sysoev igor at sysoev.ru
Thu Jul 1 10:23:14 MSD 2010

On Thu, Jul 01, 2010 at 01:48:31AM -0400, Lorin Halpert wrote:

> Using the built-in generator changes the color of the background color under
> Chrome, yet using my own blank doesn't cause this. I've attached a "known
> good" blank created in Fireworks (same byte size) so it can replace the one
> in the nginx codebase. I am under windows with no development tools so I
> can't create a patch myself but I'm able to test a new binary to validate
> that it's fixed.

The current empty GIF has 2 colors: #0: black and #1 white.
The white (#1) color is used as background and as transparent color.

The suggested GIF has two colors: #0 gray (C0C0C0) and #1 black.
The transparent color is #0 (gray). The background color is #256
and there is no such color number in the GIF table. I'm not sure
how browsers will handle this case. Probably they use just #1 color.

However, I do not understand the issue. Could you show example on
the web where built-in GIF changes background color ?

Igor Sysoev

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